In motor vehicles, a wheel cap is generally installed on an outer side of a wheel axle. The wheel cap not only covers the rigid mechanical structure of the wheel and serves as a decoration, but also protects a wheel bearing. As disclosed in U.S. Pat. Nos. 4,457,560 and 6,585,330, a wheel cap is secured onto a wheel by screws and nuts, such that when the wheel is rotated, the wheel cap will be rotated synchronously, and will not be separated from the wheel during the rotation.
In general, most wheel caps of wheels come with a brand logo of a motor vehicle or the wheel, and such arrangement not only serves as a decoration, but also achieves effect of advertising and promoting the brand of the motor vehicle or the wheel. However, the wheel caps disclosed in the aforementioned two prior arts are rotated with the wheels synchronously, so that when the wheel is still, the brand logo on the wheel cap will be rotated to an uncertain angle or position, such as an overturn angle of 90 degrees or 180 degrees from the relative correct position. As a result, the brand logo is deflective or upside down, and people cannot recognize the meaning of the brand logo on the wheel cap easily.
Further, U.S. Pat. No. 5,490,342 discloses a wheel cap comprising a fixed cover mounted onto a wheel, and a movable cover mounted onto the fixed cover, wherein the movable cover includes an axle strut for coupling with a bearing on the fixed cover, so that the movable cover and the fixed cover can be rotated axially with respect to each other, and the movable cover includes a balance weight, such that the movable cover can be maintained at a predetermined angle and position by means of the gravitation of the balance weight and the axial rotation of the bearing whether the wheel drives the fixed cover to rotate or not.